The self-organizing map was constructed using the 12,486 genes that show more than a 2-fold change in at least 1 experiment regardless of their expression level or whether the observed level of regulation is statistically significant. Each of the 12,486 genes was placed into the most appropriate expression group (node on the selforganizing map) for that gene, regardless of the statistical significance of its regulation. Every gene is present in only one expression group, although some genes may overlap substantially with genes of other expression groups.